January 30, 1903.] 



SCIENCE. 



171 



the wind direction and velocity, and the 

 solar radiation have each one maximum 

 and one minimum ; the barometric pres- 

 sure, the vapor tension, the electric po- 

 tential have two maxima and two minima. 

 There has been great difficulty in account- 

 ing for the simultaneous occurrence of 

 these two types. Lord Kelvin advocates 

 the theory of a forced semidiurnal dj^namic 

 wave in the atmosphere, and Dr. J. Hann, 

 after vainly tiying to reconcile the tem- 

 perature and the pressure cui'Ves, appears 

 obliged to accept Kelvin's view. Recent 

 observations in the lower strata of the 

 atmosphere with kites and balloons show 

 that the surface double-wave becomes a 

 single-wave at altitudes which are very 

 moderate, about that of the cumulus 

 clouds. It becomes, then, necessary to 

 account for the transformation of the 

 double- into the single-wave within these 

 strata. It is done in this paper by discuss- 

 ing the action of the solar radiation in the 

 atmosphere, and upon the earth's surface; 

 and especially by indicating the effect of 

 the outgoing terrestrial radiation upon the 

 aqueous vapor sheet. This rises and falls 

 daily, and it is shown by the method of 

 volume contents of dry air and aqxieous 

 vapor that the known facts harmonize 

 closely with the new theory as set forth 

 bj' the author. Incidentally, a discussion 

 of the normal solar spectrum energy curves 

 at different temperatures, and the observed 

 depleted energy curve as given by Pro- 

 fessor Langley, indicates that the solar 

 constant is probably about 4.0 gram calories 

 and that the temperature of the solar photo- 

 sphere is not far fi-om 7500° C. 



The Construction of a Sensitive Galvanom- 

 eter. C. G. Abbott, Smithsonian Insti- 

 tution. With an introduction by S. P. 

 Langley, Smithsonian Institution. 

 For the last seven years the galvanom- 

 eter of the bolometric apparatus of the 



Smithsonian Astrophysical Observatory has 

 been frequently modified in the interest 

 of greater working sensitiveness. Starting 

 in 1896 with a four-coil instrument of 

 about 25 ohms resistance and with a com- 

 puted constant of 2 X 10"" amperes for 

 a ten-seconds single swing, with scale dis- 

 tance one meter, it has now become a six- 

 teen-coil instrument of only 1.6 ohms I'esist- 

 anee and with an actual working constant 

 at ten-seconds single swing of 5 X 10"^^ 

 amperes for scale distance of one meter. 

 In practice, however, the scale distance is 

 four meters, and one tenth division is 

 readable, so that a current of about 

 1 X 10-^^ amperes can be measured. The 

 paper of Mr. Abbott describes the succes- 

 sive steps by means of which this change 

 has occurred. These include modifications 

 of the construction of support, case, sur- 

 roundings, coils, needle system and mode 

 of reading. 



The Condition Governing the Coherence of 

 Metals when there is an Electrical Dis- 

 charge between them: Carl Kinsley, 

 University of Chicago. 

 In the many studies of coherence that 

 have been made there has usually been 

 a complete disregard of several of the 

 conditions controlling coherence. It is 

 necessary to know not only the potential 

 at which the discharge takes place, but also 

 the quantity of the discharge. The dielec- 

 tric between the metals and its condition as 

 to temperature and pi'essure is also of 

 great importance. The condition of the 

 surfaces, their size, shape and distance 

 apart, must be known. 



An apparatus enabling distance of the 

 order of one four-hundredth of a wave- 

 length of light to be measured was used. 

 This made it possible to carry on the ex- 

 perimental work within distances such as 

 those found in the usual form of coherer. 



